1. Field of the Invention
This device relates to a rotor shaft sealing mechanism for synthetic resin material kneading machines or extruders. More particularly it relates to an improved rotor shaft end sealing mechanism in continuous kneading machines or extruders in which raw materials such as rubber and plastics continuously supplied through the inlet at one end of the machine are kneaded while they move past the mixing chamber toward the outlet at the other end by the internal pressure developed in the mixing chamber.
2. Description of the Prior Art
A reverse screw type shaft sealing mechanism (FIG. 1), a gland packing type shaft sealing mechanism (FIG. 2) and a spring-loaded type shaft sealing mechanism (FIG. 3) have been proposed as the rotor shaft end sealing mechanism in kneading machines for rubber and plastic materials.
The reverse screw type shaft sealing mechanism, as shown in FIG. 1, has a construction such that a mixing rotor installed in a mixing chamber 1 of the kneading machine has its end 2a threaded with reverse screw 3. In this type of shaft sealing mechanism, when powder is used as the mixed material, it is very likely to leak out by the pulsating pressure developed in the mixing chamber 1. This mechanism also has the drawback that when the viscosity of the melted material becomes low, the melted material is likely to leak out.
These disadvantages are considered to result from the reverse screw being designed to seal highly viscous melted materials.
The gland packing type shaft sealing mechanism, shown in FIG. 2, has a construction such that the rotor shaft 2 installed in the mixing chamber 1 of the kneading machine has around its shaft end 2a, gland packing materials 4 which are received in a housing member 5 and are held secured by a retainer member 7 bolted into the housing 5 by fixing element 6. In this sealing mechanism, the gland packing material 4 can only serve as a stuffing material and does not provide a sufficient seal against highly viscous materials, so that leaks will occur a short time after the machine has begun operating. This type of sealing mechanism also has the disadvantage that the gland packing material 4 does not have sufficient flexibility to follow the deflections of the rotor shaft 2.
The spring-loaded type shaft sealing mechanism, shown in FIG. 3, has a construction such that the rotor shaft 2 installed in the mixing chamber 1 has around its end 2a a ring 8 which presses against the end surface 2b of the rotor shaft 2. This construction has the drawback that the metallic members slide against each other thereby producing metal particles which may get into the mixing chamber and pollute the material being kneaded. In some cases, lubricating oil is used for the sliding portions to eliminate this problem (at arrow). However, this poses still another serious problem; that is, the lubricating oil itself will get into the mixing chamber and pollute the material being kneaded.
Though not shown in the drawings, there has also been proposed a shaft sealing mechanism which is the combination of the reverse screw type shaft sealing mechanism and the gland packing type shaft sealing mechanism. This mechanism can prevent the leakage of powder to some extent. However, the material that has leaked through the reverse screw portion cannot be prevented from leaking further by the gland packings.
As can be seen in the foregoing, the conventional shaft sealing mechanisms have drawbacks, and it is desirable to provide a shaft sealing mechanism which incorporates the following features.
(A) The sealing mechanism is capable of sealing both powdered material such as rubber and plastic and melted material of high viscosity. PA1 (B) The sealing portion of the sealing mechanism is not subject to pulsating pressure. PA1 (C) The sealing mechanism can prevent the pollution of the material being kneaded by foreign substance getting into the mixing chamber. PA1 (D) The sealing mechanism is flexible enough to follow the deflection of the rotor shaft.